It seemed a routine border arrest: A car crossing from Mexico to the U.S. on March 4 had 12 pounds of cocaine hidden in the battery compartment. The driver was arrested and charged with smuggling.

But this was to turn out to be no ordinary bust. The driver was one of Tijuana’s most prominent architects, who had designed everything from an iconic art museum to a Roman Catholic cathedral, and whose fate on that day had been determined by a coin flip.

The weird tale of architect Eugenio Velázquez came to a close Monday when a San Diego federal judge sentenced the 51-year-old to six months in prison and another six months in home detention.

The judge accepted Velázquez’ contention that he was no common smuggler — but a victim of a former client who forced him at gunpoint to carry drugs across the border, and threatened to harm his family.

While that is a story heard often in federal court, Velázquez’ case is different. That’s because his story was corroborated by the government, and that in turn led to a more lenient sentence than he would have faced.

After his arrest, his wife received threatening phone calls — forcing her to go into hiding for a week.

Gunman came to his office, terrifying his employees.

In court, Velasquez acknowledged that he ought to have gone to authorities when he was pressed into smuggling — a choice he now regrets.

“I never imagined myself,” he told U.S. District Judge Thomas Whelan, “in a place such as this.”

Velázquez’s projects include El Cubo, the art gallery at the Tijuana Cultural Center, and two projects under construction: the Roman Catholic cathedral and Centro Estatal de las Artes, an arts center at Morelos Park.

Jeremy Warren, his lawyer, said that Velázquez believed he had to comply with the threat to protect his family.

In a legal filing for the sentencing, Warren wrote that Velásquez had agreed to do work on a house of an unidentified client in Mexico. But he said that when Velázquez said he was uneasy about Tijuana’s violence, the client said he could provide an escort each time he crossed the border.

The same client also provided security for an unidentified friend of Velázquez, a doctor, who also crossed the border regularly.

When the architecture job was finished, the client told Velázquez and the doctor they owed him for the security.

When they balked at paying $40,000, the client pulled out a gun and told them they would have to smuggle drugs instead. He flipped a coin, with the loser to go first. Velázquez lost.

Velázquez pleaded guilty in June to knowingly and intentionally importing the cocaine, a charge that carries a minimum 10-year sentence under federal guidelines. He had no earlier criminal record.

But his story was backed up. The doctor who witnessed the threat corroborated it, as did employees at his office.

Velázquez’s arrest followed the arrest of Maximino Melchor, an aspiring, 23-year-old classically trained singer in Tijuana. Melchor pleaded guilty in state court to transporting 44 pounds of methamphetamine in September.

Melchor’s lawyers also said their client was forced into smuggling by threats against his family.

Velázquez, a U.S. citizen, was a tempting target because he had been cleared by a U.S. government background check to get a SENTRI card, a pass that allows trusted travelers to cross the border faster.

Outside court, he hugged a large group of family and friends who came to support him. He said he was relieved that the judge and the government believed his story. Prosecutors had sought a term of 30 months in prison but did not object to the lowered sentence.

“He was forced into doing this,” Warren said. “We’re very pleased the judge and the government recognized the truth of what happened here.”